Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$172.33	5.237%	$181.3549	$181.35	$181.35	$181.40
Purchase #2	$131.34	9.564%	$143.9014	$143.90	$143.90	$143.90
Purchase #3	$169.62	3.192%	$175.0343	$175.03	$175.05	$175.00
Purchase #4	$146.34	13.578%	$166.21	$166.21	$166.20	$166.20
Purchase #5	$154.25	10.315%	$170.1609	$170.16	$170.15	$170.20
Purchase #6	$238.62	7.224%	$255.8579	$255.86	$255.85	$255.90
Purchase #7	$148.85	11.256%	$165.6046	$165.60	$165.60	$165.60
7 purchase totals =	$1,161.35		$1,258.1240	$1,258.11	$1,258.10	$1,258.20